The increased CD38 expressed by lymphocytes infected with HIV-1 is a fully active NADase

Altered phenotype of regulatory T cells associated with lack of human immunodeficiency virus (HIV)-1-specific suppressive function

Mechanisms by which CD4+ regulatory T cells (T(regs)) mediate suppression of virus-specific responses remain poorly defined. Adenosine, mediated via CD39 and CD73, has been shown to play a role in the action of murine T(regs) . In this study we investigate the phenotype of T(regs) in the context of human immunodeficiency virus (HIV)-1 infection, and the function of these cells in response to HIV-1-Gag and cytomegalovirus (CMV) peptides. Phenotypic data demonstrate a decrease in forkhead box transcription factor 3 (FoxP3+) T(reg) numbers in the peripheral blood of HIV-1+ individuals compared to healthy controls, which is most pronounced in those with high HIV-1 RNA plasma load. Due to aberrant expression of CD27 and CD127 during HIV-1 disease, these markers are unreliable for T(reg) identification. The CD3+ CD4+ CD25(hi) CD45RO+ phenotype correlated well with FoxP3 expression in both the HIV-1+ and seronegative control cohorts. We observed expression of CD39 but not CD73 on T(regs) from HIV-1+ and healthy control cohorts. We demonstrate, through T(reg) depletion, the suppressive potential of T(regs) over anti-CMV responses in the context of HIV-1 infection; however, no recovery of the HIV-1-specific T cell response was observed indicating a preferential loss of HIV-1-specific T(reg) function. We propose that before immunotherapeutic manipulation of T(regs) is considered, the immunoregulatory profile and distribution kinetics of this population in chronic HIV-1 infection must be elucidated fully.

The reconstitution of the thymus in immunosuppressed individuals restores CD4-specific cellular and humoral immune responses

Infection with HIV-1 frequently results in the loss of specific cellular immune responses and an associated lack of antibodies. Recombinant growth hormone (rGH) administration reconstitutes thymic tissue and boosts the levels of peripheral T cells, so rGH therapy may be an effective adjuvant through promoting the recovery of lost cellular and T-cell-dependent humoral immune responses in immunosuppressed individuals. To test this concept, we administered rGH to a clinically defined group of HIV-1-infected subjects with defective cellular and serological immune responses to at least one of three commonly employed vaccines (hepatitis A, hepatitis B or tetanus toxoid). Of the original 278 HIV-1-infected patients entering the trial, only 20 conformed to these immunological criteria and were randomized into three groups: Group A (n = 8) receiving rGH and challenged with the same vaccine to which they were unresponsive and Groups B (n = 5) and C (n = 7) who received either rGH or vaccination alone, respectively. Of the eight subjects in Group A, five recovered CD4 cellular responses to vaccine antigen and four of these produced the corresponding antibodies. In the controls, three of the five in group B recovered cellular responses with two producing antibodies, whereas three of the seven in Group C recovered CD4 responses, with only two producing antibodies. Significantly, whereas seven of ten patients receiving rGH treatment in Group A (six patients) and B (one patient) recovered T-cell responses to HIVp24, only two of six in Group C responded similarly. In conclusion, reconstitution of the thymus in immunosuppressed adults through rGH hormone treatment restored both specific antibody and CD4 T-cell responses.

Changes in T-cell subsets in HIV-HCV-coinfected patients during pegylated interferon-alpha2a plus ribavirin treatment

BACKGROUND

We evaluated the effect of different doses of pegylated interferon (PEG-IFN)-alpha2a/ribavirin (RBV) on several T-cell activation markers in HIV-HCV-coinfected patients and their relationship with changes in plasma HCV RNA.

METHODS

Frozen peripheral blood mononuclear cells (PBMCs) from 22 patients receiving two different PEG-IFN-alpha2a schedules were analysed by six-colour flow cytometry. Cell-surface expression of CD38 was quantified. HIV and HCV viral loads, as well as absolute CD4+ and CD8+ T-cell counts, were recorded during the follow up (72 weeks).

RESULTS

PEG-IFN-alpha2a/RBV treatment decreased the absolute numbers of CD8+ and CD4+ T-cells. The decrease in CD8+ T-cells was more pronounced, resulting in increased percentages of CD4+ T-cells. Percentages of naive/memory CD4+ T-cell subsets remained unchanged, although the percentage of CD38+CD45RO+ cells significantly increased. By contrast, the CD8+ T-cell compartment significantly reduced the percentage of CD45RO+ cells and HLA-DR+ cells, whereas the percentage of CD38 expressing cells was increased because of a significant increase in cell-surface CD38 expression. Changes in CD8+ T-cells were similar for both PEG-IFN-alpha2a/RBV doses, but high doses induced more severe perturbations in CD4+ T-cells. All changes returned to baseline levels after treatment cessation and, except for the loss of naive CD4+ T-cells, were not associated with virological response.

CONCLUSIONS

Transient lymphopaenia induced by PEG-IFN-alpha2a/RBV differentially affects T-cell subsets. Activated HLA-DR+ and CD45RO+ cells were selectively reduced in peripheral blood, whereas CD38 expression was up-regulated mainly in memory cells. Increasing PEG-IFN-alpha2a/RBV doses mainly affect CD4+ T-cells but failed to modify clinical outcome.

Evolution and function of the ADP ribosyl cyclase/CD38 gene family in physiology and pathology

The membrane proteins CD38 and CD157 belong to an evolutionarily conserved family of enzymes that play crucial roles in human physiology. Expressed in distinct patterns in most tissues, CD38 (and CD157) cleaves NAD(+) and NADP(+), generating cyclic ADP ribose (cADPR), NAADP, and ADPR. These reaction products are essential for the regulation of intracellular Ca(2+), the most ancient and universal cell signaling system. The entire family of enzymes controls complex processes, including egg fertilization, cell activation and proliferation, muscle contraction, hormone secretion, and immune responses. Over the course of evolution, the molecules have developed the ability to interact laterally and frontally with other surface proteins and have acquired receptor-like features. As detailed in this review, the loss of CD38 function is associated with impaired immune responses, metabolic disturbances, and behavioral modifications in mice. CD38 is a powerful disease marker for human leukemias and myelomas, is directly involved in the pathogenesis and outcome of human immunodeficiency virus infection and chronic lymphocytic leukemia, and controls insulin release and the development of diabetes. Here, the data concerning diseases are examined in view of potential clinical applications in diagnosis, prognosis, and therapy. The concluding remarks try to frame all of the currently available information within a unified working model that takes into account both the enzymatic and receptorial functions of the molecules.

A single measurement of CD38CD8 cells in HIV+, long-term surviving injecting drug users distinguishes those who will progress to AIDS from those who will remain stable

This study compares the predictive power of a single measurement of CD8+CD38+, CD8+CD45RO+ or CD8+CD38+CD45RO+ subpopulations in predicting progression to AIDS in a cohort of HIV+ long-term surviving injecting drug users. The results showed that both the total CD8+ percentage, and the CD8+CD38+ and CD8+CD38+CD45RO+ subpopulations of cells all individually predicted progression to AIDS. In combination with CD4, only the CD8+CD38+ subpopulation enhanced the predictive power of the CD4 percentage alone. The CD8+ percentage correlated negatively with the CD4 percentage and the CD8+CD45RO+ subpopulation did not predict disease progression. The proportion of CD8+CD38+ cells identified which patients with a moderate CD4 level were more likely to progress to AIDS, and conversely, which patients with a low CD4 count were likely to remain clinically stable. The results were consistent irrespective of whether time was measured from the date of seroconversion, or from the date of the test. This study is the first to measure these markers in HIV-infected injecting drug users, and in long-term survivors. The results demonstrate the considerable added value of the CD8+CD38+ cell percentage over the CD4 count alone, in predicting HIV clinical progression.